It is well known in the art of thermometers to use a bimetal coil which responds to changes in temperature by coiling or uncoiling. Typically, in a thermometer using a bimetal coil, the temperature response of the bimetal coil actuates an indicator means (for example a pointer or needle). The displacement of the indicator may be measured against a background of a graduated scale to obtain a temperature reading.
In the prior art a thermometer of the type discussed above typically would have been manufactured as an integral unit in which a bimetal coil, arbors and associated components interact with one another in such a way that the specifications, tolerances and other design criteria are inextricably intertwined. Therefore, the element components are not readily adaptable or transferable to other devices. Examples of such prior art devices are disclosed in Hastings, U.S. Pat. Nos. 2,123,532 issued July 12, 1938, Argabrite, 2,701,964 issued Feb. 15, 1955, and Andrews, 3,851,529, issued Dec. 3, 1974. Manufacturers of thermometers must continually respond to changing market appetites by introducing new designs of thermometers which follow decorating trends. There is perceived, therefore, a need for a universal thermometer movement which will be readily adaptable to drive a variety of designs. Accordingly, thermometer design and manufacture can be done by persons mainly interested in the aesthetics rather than in the mechanics of thermometers.
Thermometers utilizing a bimetal coil may require calibration from time to time. Typically, in thermometers utilizing a bimetal coil, one end of the coil is anchored to a fixed reference point while the other end is connected to movable indicating means. As discussed in Berleyoung, U.S. Pat. No. 3,818,763, issued June 25, 1970, the anchoring of the coil to the fixed reference point may be inaccurate, resulting in poor calibration and erroneous readings. Berleyoung suggests that the calibration problem might be resolved by anchoring the inner end of the coil to a rotatable hub. A flanged extension is provided at the outer (free) end of the coil. The flanged extension undergoes displacement in an arc as the coil responds to changes in temperature. The flanged extension itself is used as the thermometer indicator means to be read in relation to a dial. The device can be calibrated by rotating the hub (and associated coil) to the desired reading.
The device disclosed by Berleyoung does not however allow for the use of indicating means which rotate about a fixed point, such as pointers or needles, as opposed to indicating means which are displaced in an arc, since the "free" outer end of the coil element of Berleyoung undergoes translation rather than rotation. It follows also that the Berleyoung device does not allow calibration of such indicating means. Moreover, it is thought that such a device is not as readily adaptable to a universal thermometer movement since the translational movement is more limited than rotational movement from the point of view of the range of aesthetic designs which may be developed about it.